Gravitar 4-12-83

Although this prototype is dated four days later, it
appears to have some slight differences. They appear to be mostly minor tweaks to the level structures designed to make the game slightly easier. Perhaps the programmer thought that some levels were too hard? It's unknown why Atari released the slightly harder version as Gravitar is an insanely hard game to begin with.

Prototype
Differences

Your ship faces up when entering the reactor base instead of down

The far right planet in the second solar system has minor changes to one of its walls to make them less thick. This makes it slightly easier to move around.

The top most planet in the third solar system has minor changes to one of its walls to make them less thick. This makes it slightly easier to move around.

Notice how your ship points up?

In the final version it always points down

The passage on the left side is a little wider in the prototype

In the final version the wall is thicker making the passage harder to navigate